difference between Speedometer and VSSB readings?

[noelb]

I have found a difference between the readings of the VSSB and the spedometer. the speed reading I get from communication with the PCM will give me a reading of - say 40 mph while the Speedo will read about 43 mph. I guess the PCM gets it's reading from the VSSB right?

This difference is probably due to speedo error, but I was just asking to see if this would be most likely the case.

I was wondering whether adjusting the VSSB will correct this difference or if the only way to correct is to have the Speedo Re-Calibrated?

Is this difference likely to cause an issue with the ABS?

[DennisG01]

I can't say about the ABS, although if I ventured a guess I would say it wouldn't interfere.

As far as which component is showing the correct speed, use a handheld GPS to verify your speed, first. Just as a double check.